Lip seals are frequently used between two relatively rotatable members to provide a seal between two areas having a pressure differential. The lip seal is so formed that the higher pressure forces the lip on one member into engagement with the other member, which will usually be that exhibiting the greater rotational tendency. The frictional engagement of the lip seal on the other member produces drag on that member as it rotates, and more rotational force or torque must be expended to overcome this drag. In most cases, this drag is not an item of concern; however, where the available torque driving the rotating member is limited, this drag may become of significant concern.
Space suits, as exemplified by U.S. Pat. No. 3,636,564, generally include rotatable joints to permit natural body motion. Present space suits make use of ball bearings with lip seals to provide rotary motion for the arms, legs, head and torso, and to provide for bending motion at various body joints. A problem arises in sealing the space between the two components of the bearing assemblies provided at these joints, and low torque is required for ease of movement and to reduce fatigue during movement.
Moreover, in a space suit, all rotatable joints of the suit are not in parallel planes, and low bearing torque is absolutely essential, since sections of the space suit must be made to rotate by bending motion of the human body. High torque multiples the bending force required to flex the joint. As a result, it has become apparent that low torque bearings would be extremely beneficial for use in space suits.
It has been determined that approximately ninety-nine percent of the torque in the bearings presently used on space suits comes from the seal which is required to maintain the suit pressure wherever a bearing is used. Space suits are pressurized and a seal is required to prevent the passage of the pressurized fluid through the bearing races, by providing a lip or the like in that space on one member of the bearing assembly which bears on an opposing cylindrical surface. This force is made up of two components--an initial force caused by the deflection of the lip from its at rest position, i.e. the position it would take if there was no opposing cylindrical surface for it to bear against, and the force caused by the pressure of the fluid being contained pressing on the lip and forcing it against the opposing surface.
It is an object of the present invention to provide a bearing assembly for use in environmental control suits utilizing between relatively rotatable members a novel, improved lip seal which is highly effecting in minimizing leakage thereby of fluid under pressure and which requires relatively low torque to effect rotational movement.
It is also an object to provide such bearing assembly with a lip seal which has portions of differing flexural characteristics to flex depending upon the pressure differential and thereby the deflection required to provide the sealing action.
A specific object is to provide an environmental suit for a human being which employs bearing assemblies with novel lip seals at various joints to provide excellent sealing characteristics while minimizing the torque required to effect relative movement of the surfaces being sealed.